/*
 * Created on 17 Jul 2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package org.gudy.azureus2.core3.util;

import java.util.LinkedList;

public class AsyncDispatcher {
    private String name;
    private AEThread2 thread;
    private int priority = Thread.NORM_PRIORITY;
    private AERunnable queue_head;
    private LinkedList<AERunnable> queue_tail;
    private AESemaphore queue_sem = new AESemaphore("AsyncDispatcher");

    private int num_priority;

    private int quiesce_after_millis;

    public AsyncDispatcher() {
        this("AsyncDispatcher", 10000);
    }

    public AsyncDispatcher(String name) {
        this(name, 10000);
    }

    public AsyncDispatcher(int quiesce_after_millis) {
        this("AsyncDispatcher", quiesce_after_millis);
    }

    public AsyncDispatcher(String _name, int _quiesce_after_millis) {
        name = _name;
        quiesce_after_millis = _quiesce_after_millis;
    }

    public void dispatch(AERunnable target) {
        dispatch(target, false);
    }

    public void dispatch(AERunnable target, boolean is_priority) {
        synchronized (this) {

            if (queue_head == null) {

                queue_head = target;

                if (is_priority) {

                    num_priority++;
                }
            } else {

                if (queue_tail == null) {

                    queue_tail = new LinkedList<AERunnable>();
                }

                if (is_priority) {

                    if (num_priority == 0) {

                        queue_tail.add(0, queue_head);

                        queue_head = target;

                    } else {

                        queue_tail.add(num_priority - 1, target);
                    }

                    num_priority++;

                } else {

                    queue_tail.add(target);
                }
            }

            if (thread == null) {

                thread = new AEThread2(name, true) {
                    public void run() {
                        while (true) {

                            queue_sem.reserve(quiesce_after_millis);

                            AERunnable to_run = null;

                            synchronized (AsyncDispatcher.this) {

                                if (queue_head == null) {

                                    queue_tail = null;

                                    thread = null;

                                    break;
                                }

                                to_run = queue_head;

                                if (queue_tail != null && !queue_tail.isEmpty()) {

                                    queue_head = queue_tail.removeFirst();

                                } else {

                                    queue_head = null;
                                }

                                if (num_priority > 0) {

                                    num_priority--;
                                }
                            }

                            try {
                                to_run.runSupport();

                            } catch (Throwable e) {

                                Debug.printStackTrace(e);
                            }
                        }
                    }
                };

                thread.setPriority(priority);

                thread.start();
            }
        }

        queue_sem.release();
    }

    public boolean isQuiescent() {
        synchronized (this) {

            return (thread == null);
        }
    }

    public int getQueueSize() {
        synchronized (this) {

            int result = queue_head == null ? 0 : 1;

            if (queue_tail != null) {

                result += queue_tail.size();
            }

            return (result);
        }
    }

    public void setPriority(int p) {
        priority = p;
    }

    public boolean isDispatchThread() {
        synchronized (this) {

            return (thread != null && thread.isCurrentThread());
        }
    }
}
